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print meter

DREW WILEY said:
And what a really good easel densitometer tells you is those f-stop settings on many enlarging lenses are NOT always of truly consistent intervals.
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Don’t you know it! I used to think I was losing my mind when one click down and double the time didn’t give me the same results.

The photomultiplier tubes quickly reveal you are right. Lens clicks aren’t consistent
 
Bill Burk said:
Don’t you know it! I used to think I was losing my mind when one click down and double the time didn’t give me the same results. The photomultiplier tubes quickly reveal you are right. Lens clicks aren’t consistent
Click to expand...

Yes!
I measured the accuracy of the click-stops on my lenses using the DarkroomAutomation meter, and discovered two things (about my lenses anyway):
1. Accuracy from wide open to 1st stop is poor.
2. Actual f-stop at a click-stop will differ based on the direction you were moving the ring (stopping down versus opening up).

Consequently, I have two suggestions:
1. Always reach a click while stopping down (you probably don't expose wide open, so that stop doesn't matter). Doing so ensures consistency when you want to make a another identical print two weeks later.
2. Don't change the f-stop after you have decided the exposure.

Mark Overton
 
Well Bill, my easel densitometer is well beyond the photomultiplier era, but similar concept : Don't take anything for granted.
But my Apo Nikkor f/9 process lenses, which I often use for enlarging, have their f-stops marks spot on, incrementally. Those were originally quite expensive and designed for commercial graphics standards way more stringent than general photography standards; and no hard click stops, just clean finely engraved lines.
 
To each their own - either approach will work, and either approach will be frustrating if your exposure and film development regimes are not consistent. I start with maximum black time as that's how I work for alternative process printing - get the shortest time possible to achieve maximum black, then adjust your contrast to bring the rest of your tones where you want them. It also leads to consistency because once you get your maximum black, and your contrast dialed in, then every single print is the same amount of time. Regardless, it's a learning process and not a one-and-done thing.
 
My 5108 vents into the darkroom, it does make the process rather noisy. The biggest Durst I've seen personally is one of the 5x4 machines, not sure of the wattage however.
 
Anyway nothing forbids to convert f stops in seconds of exposure if
one doesn't want to use f stops and work only with the best lens diaphragm.
I just think that even a non strictly professional tool like ilford exposimeter
can be useful to save on paper and find a starting point to make test strips .
 
How far off is the wide open to 1st stop? What is the differential at each f-stop when stopping down rather to opening up? What lenses are you using that exhibit these errors?
 
F-stop timing does not use actual f-stops on the lens, just the exposure interval equivalent to an f-stop or fraction thereof. So the accuracy of your lens stops doesn't really matter.
 
faberryman said:
How far off is the wide open to 1st stop?
Click to expand...

Depends on the lens. My experience is ~1/3 of a stop. Assuming the f4.0 aperture marking on a lens is accurate then an f2.8 lens is really ~f3.1. The f-stop differences on the lens from there on out are very accurate. As no one (well, amost no one) uses the maximum aperture on an enlarging lens it's no great loss; I chalk it up to marketing excess
 
Some of the APO lenses are excellent wide-open. Plus the larger aperture can make focusing and composition a bit easier.
 
The aperture controls not only the AMOUNT of light passing through, but the angle of incidence, which might in turn mandate a different condenser or degree of diffusion with aperture changes. And not only is optimal sharpness controlled by specific aperture, but EVENNESS OF FIELD. Fully or nearly wide open lenses rarely provide fully even illumination. And even if that is partially corrected with a convex diffuser, you still might have to alter the percent of corner and edge burning with significant changes in the stop itself. But most people who don't know these facts probably don't use glassless carriers or have properly aligned and leveled setups anyway. One step at a time.

High end graphics lenses are a slightly different story, but not totally exempt from what I just explained. And they generally have a maximum aperture of f/9, which has already trimmed off most of the less than ideal angle or field of view. But you still need an optimized diffuser or mirror box system above the negative stage.

And there's nothing wrong with pointing these things out to a beginner, because maybe he'll want to know there is a second base and third base on playing field before one can achieve a home run.
 
I remember from reading lens tests that the wide open aperture markings are often aspirational, so I was more interested in the discrepancy in values when opening up versus stopping down. Do I understand you correctly to be saying that if you stop down to f/8 it might be f/7.9, but if you open up to f/8 it might be f/8.1. I would not have expected that level of mechanical error in the aperture.
 
Most of that would not be noticed by a beginner or intermediate printer. And many printers burn the edges of the image, so some of that is already being dealt with. But as you say, many print with misaligned stages and glassless carriers, so it is kind of outside the range of quality they will get anyway.
 
The first black and white image I ever made, though it took me about a week to figure out how to print best, was in fact a home run, outright collector quality. Beginner's luck perhaps; but I already had a background color printing, so knew some basic technique. My attitude from day one was to make the best possible prints I could, from the first day I ever laid hands on an enlarger. No, not everybody cares about that. There's nothing wrong with just having fun. But I personally would have saved a lot of time and a LOT of money over the years if someone had told me up front, when I was just beginning, the kind of things I know now, yet had to learn the hard way.

People can pick and choose from these forum threads what they need. Yeah, it can be confusing at first. But basic questions lead to multiple answers of more general applicability, just like on this thread, potentially useful to someone else down the line.
 
faberryman said:
How far off is the wide open to 1st stop? What is the differential at each f-stop when stopping down rather to opening up? What lenses are you using that exhibit these errors?
Click to expand...

I don't know. Hold on, I'll run into the darkroom and measure them.
I'm back, and the results are:

El-Nikkor 80/5.6: 1/6 stop error from wide-open to first click. Max subsequent error is about 0.03 stop. Error between 1st and last click is 0.02 stop. Max bidirectional error is 0.03 stop.
Omicron 50/2.8: Just under 0.1 stop error from wide-open to first click. Max subsequent error is about 0.1 stop. Error between 1st and last click is 0.2 stop. Max bidirectional error is 0.04 stop.​

Except for its 1/6 stop error from wide-open, the El-Nikkor has much less error than the Omicron.

What I call "bidirectional error" is the difference between click-while-closing and click-while-opening. At almost 1/20 stop, most people won't notice, but those doing critical work will want to avoid it.

Mark Overton
 
Thank you.
 
For nitpicky work, which is more common in my case than you might think, I adjust and read the light using an extremely accurate easel densitometer which reads in actual logarithmic density units. And to make time changes instead of aperture changes, if that is what I want to do, I use a simple high school math calculator with a log function. Even I know how to push buttons sometimes, even though I still don't know how to take a picture with my own Smart Phone.
 
I had to go back to page one and read the OP's original question. I guess the thread has digressed a bit...

About using an enlarging exposure meter though: Personally, I never have and don't plan to. I don't think I would even if someone gave me one, because I'm really happy with, and fast at, determining my exposure using test strips. They cost less than the enlarging meter as well.

As for how to make the most useful test strip (one of the topics of the thread now): Using a linear timing will work just fine, but has the disadvantage that the more-dense stripes on the strip get progressively less exposure difference. Fred Picker touted his three-second test strip. He had his timer set on three seconds and just stepped on the footswitch a lot when making linear-timed test strips as well as building up exposure on prints (a good way to wear out a footswitch IM-HO).

It's pretty easy to understand that if you make a test strip in, say, three-second intervals that the exposure increase between the first strip with a three-second exposure and the second strip with two three-second exposures (six seconds total) is going to be a 100% or a one-stop difference. The next strip gets a total of nine seconds, only a 50% increase from the preceding strip. Note, however, that this is NOT a half-stop increase, rather a bit more. Adding half a stop to 9 seconds gets you approx. 8.5 seconds; close but not quite 9 seconds.

On to the next stripe, which gets 12 seconds total, a 33% increase (or just over a third stop increase; the real third-stop value would be approx. 11.34 seconds).

Subsequent stripes on the test strip get less and less exposure increase, which makes evaluating the test strip at longer exposures more and more difficult. By the time you get to 24 seconds, that stripe is only about 14% more exposed than the previous one. (FYI, that works out to just a bit more than a sixth of a stop). The difference between the 30 and 33-second stripes would only be 10%, or only about a seventh of a stop.

It makes a heck of a lot more sense to expose a test strip in progressively longer exposure intervals, preferably in a sequence that had the same exposure change between each stripe. F-stop timing does this, and if you use the whole-number sequence that Matt suggests (post #69), then there's not a real problem, especially since most photographers have the f-stop sequence memorized.

If you want to get more precise with f-stops, though, you quickly move in to the realm of fractions (e.g., f/5.6 or f/2.8) which makes calculating intermediate exposures a bit trickier. Plus, who has the f-stop sequence memorized in 1/6-stop increments? I know I don't. If you go down the rabbit hole of actually calculating the intervals, then you need to deal with roots of 2 and need a calculator or a fancy f-stop timer.

I prefer to work with percentages. They are easy to figure in your head and do the same job as f-stops. 10% of a 20-second exposure is two seconds; 5% is one second, 2.5% is half a second, at which point you are making an undetectable change to your print, or one that could be more easily controlled by increasing your print development time a bit.

As for test strips, I like a strip in 30% increments as follows (in approximate values).

To get total time: --- 10 --- 13 --- 17 --- 22 --- 29 --- 38 --- 49
Add a strip with: -----10 ---- 3 ----- 4 ---- 5 ----- 7 ----- 9 --- 11

I always start with 10 seconds, and just have to remember "3 - 4 - 5 - 7 - 9 - 11." I've got this posted by the enlarger too. If you want different increments, say 20%, or 25%, they are easy to figure too.

Then, when making changes to a print exposure, I'll add or subtract a percentage. Say I've found that my 22-second stripe is too light and my 29 second strip is a bit dark. I'll start with an intermediate value, say 27 seconds, and make a print. If that's still a bit off, say a tad too dark, I'll subtract 10% or so. 10% is 2.7 seconds, I'll round that to 3 seconds and make a print at 24 seconds. Or maybe I'll only need a small change, approximately 5%, but I don't waste time calculating with fractions of a second, I'll just take half of that rounded-off 10% value, or 1.5 seconds. But that pesky half-second won't make any real difference to a print exposure that long, so I'll use a change or either one or two seconds depending on which way I want to tweak the print. I don't need to get any more precise than that for black-and-white printing as far as exposure times go. If I really need to make smaller changes to a print than 5% or so, I'll do that with development time.

All this is really easy to figure in your head when working; a lot easier than calculating what a 1/6-stop change for a 27-second print exposure would be unless you've got an f-stop timer handy. I don't, I use a metronome. I like low-tech.

I found it easy to get used to visualizing what a percentage difference will look like when printing. One would have to do the same with f-stop timing too, since changes in print exposure do not correlate to the typical change in film exposure for a given f-stop value.

So, for the OP, and with all due respect to those who find f-stop timing a good tool and own f-stop timers, I recommend making test strips in intervals that increase by a given percentage and not bothering with enlarging exposure meters for the time being. They certainly aren't necessary for doing even the finest work, and not needed to sart making good prints right away. The better tools are a good understanding of how the process works and patience.

Best,

Doremus
 
All the best Doremus, that’s great advice! Happy New Year, maybe this weekend we’ll share more ideas.

I got a few gadgets to see how they may be best employed. So the Beseler PM2M gives me one point of reference after I get a good print. I can find an appropriate tone and set the dial to how many seconds I used for that good print. More memory channels would be a good thing. I use the C-M-Y-White channels of a module for a paper/grade. One channel for “shadow”, one for “gray” and one for “highlight.” Amusingly I cannot use the Cyan channel because my teal Aristo grid light is significantly blocked by the filter for that channel.

Now all this does for me is get me to the point where my first test strip gives me something to see.

It can save me the frustration of making that first test strip and being “off by two stops”. That is all I want the thing to do for me. And I am liking it for that. I picked up a few modules already and might get another… just to have one for each of my papers. In the old days that would be expensive but the modules pop up for twenty bucks from time to time, and that’s a cup of coffee here.

I am seriously considering memorizing different exposures for my test strip series, because I never go too dark and too light. I may jump the ends in a series like 100, 50, 40, 32, 25, 20, 10.

Set timer to 50 and hit it twice for first section, then start moving my usual 10, 8, 7, 5. But then do a 10.

Whole stop, several third stops, whole stop.

I am going to try that
 
The best tool is you eye. Make the print look like you want it to, damn the meters. Unless you are printing for others, you are better off with a well-trained eye and experience than some measuring devices or equipment.
 
Bill,

Except for maybe when I haven't printed for a long time or am using materials new to me, I rarely have a first test strip that doesn't have adequate information on it. My sequence of between 10 and 49 seconds does the job fairly well, but if I'm in doubt, I'll add a shorter (say 7-second) and a longer (say 64-second) stripe to my test strip. If I find I need to change print contrast significantly from what I started with, then I'll make a second test strip. After that, I make whole prints and refine from there. It's the small exposure and contrast changes and the manipulations and the bleaching that make the real difference anyway.

Best and Happy New Year too!

Doremus
 
I think there is more to a meter than just making quick test straps

You should be able to calculate dodge burn times for parts of image too at your chosen paper grade.

It should be able to guide you in development times for your negatives if say most of Yr roll film was shot in high or low contrast scenes and you want those types of scenes to print at grade x in the future.

I have one but due to circumstances I've never used it but that was how I understood you could also use it too. It's not going to do anything you can't do yourself through trial and error or experience but as a tool there should be more to it than just making test strips
 

2 x 3 second exposures is not twice 1 x 3 second exposure though.

If you compare 2 x 3 second exposures with 1 x 6 second exposure then 2 x3 seconds should be lighter
 
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